1. Field of the Invention
The present invention relates to a suspension for an automotive vehicle and, more particularly, to the structure of a suspension cross member for supporting a suspension arm which connects a wheel support and a vehicle body.
Rear wheel suspension systems for automotive vehicles are supported by a frame to which a vehicle body is bolted or otherwise secured at various points. Such a frame typically includes a pair of side members or frame portions, disposed on opposite sides of the vehicle body and extending in a lengthwise direction of the vehicle body, and front or first and rear or second cross members, connected to the side members. The first cross member is curved upwards at its middle portion so that at least part of a rear axle differential is placed below the first cross member. Additionally, a rear wheel suspension system typically has an A-type upper and trailing arms, pivotally supported by the side frame, and a lower arm, pivotally supported by the front cross member.
2. Description of Related Art
To describe a practical prior art rear wheel suspension support structure, reference is made to FIG. 1. As shown in FIG. 1, a body frame, to which a vehicle body is bolted or otherwise secured at various points, includes a pair of, or left and right, side members or frames a, disposed on opposite sides of the vehicle body. Each of the left and right side frames extends in a lengthwise direction of the vehicle body. The body frame also includes front or first and rear or second cross members b and c, extending in a transverse direction of the vehicle body and connected to the side members a. The front cross member b is curved upwards at its middle portion so as to place part of a rear axle differential i below the curved front cross member b. Each rear wheel suspension typically has an A-type upper arm d, a trailing arm e and a pair of lower arms f and g for each rear wheel. Each upper arm d is pivotally mounted, at its rear end, on one of the side frames a. Each trailing arm e is pivotally mounted, at its front end, on one of the side frames a. Each lower arm f is pivotally mounted, at its rear end, at an underside of a portion, adjacent to the curved middle portion, of the front cross member b. Each lower arm g is pivotally supported, at its rear end, by a sub-member h, which extends from the rear end of one of the side frames a.
A front cross member of a rear wheel suspension support structure of this kind is typically heavy in weight and, therefore, unavoidably increases the weight of the vehicle body. Using a lightweight front cross member in a vehicle body frame, however, lowers the structural rigidity of the vehicle body in its transverse direction. Thus, it is difficult to realize a lightweight vehicle body, which is one object of recent car designs.